Tissue-Infiltrating Neutrophils Constitute the Major In Vivo Source of Angiogenesis-Inducing MMP-9 in the Tumor Microenvironment

Abstract

According to established notion, one of the major angiogenesis-inducing factors, pro-matrix metalloproteinase-9 (proMMP-9), is supplied to the tumor microenvironment by tumor-associated macrophages (TAMs). Accumulated evidence, however, indicates that tumor-associated neutrophils (TANs) are also critically important for proMMP-9 delivery, especially at early stages of tumor development. To clarify how much angiogenic proMMP-9 is actually contributed by TAMs and TANs, we quantitatively evaluated TAMs and TANs from different tumor types, including human xenografts and syngeneic murine tumors grown in wild-type and Mmp9-knockout mice. Whereas host MMP-9 competence was required for full angiogenic potential of both normal and tumor-associated leukocytes, direct comparisons of neutrophils versus macrophages and TANs versus TAMs demonstrated that macrophages and TAMs secrete 40- to 50-fold less proMMP-9 than the same numbers of neutrophils or TANs. Correspondingly, the levels of MMP-9–mediated in vivo angiogenesis induced by neutrophils and TANs substantially exceeded those induced by macrophages and TAMs. MMP-9–delivering TANs were also required for development of metastasis-supporting intratumoral vasculature, characterized by ≥ 11-μm size lumens and partial coverage with stabilizing pericytes. Importantly, MMP-9–producing TAMs exhibit M2-skewed phenotype but do not express tissue inhibitor of metalloproteinases-1 (TIMP-1), a novel characteristic allowing them to secrete TIMP-1–free, neutrophil-like MMP-9 zymogen unencumbered by its natural inhibitor. Together, our findings support the notion whereby TANs, capable of immediate release of their pre-stored cargo, are the major contributors of highly angiogenic MMP-9, whereas tumor-influxing precursors of macrophages require time to differentiate, polarize into M2-skewed TAMs, shut down their TIMP-1 expression, and only then, initiate relatively low-level production of TIMP-free MMP-9 zymogen.

Identification of an Endogenously Generated Cryptic Collagen Epitope (XL313) That May Selectively Regulate Angiogenesis by an Integrin Yes-associated Protein (YAP) Mechano-transduction Pathway

“…ECM remodeling occurs as an early event during angiogenesis and multiple proteolytic enzymes, including MMPs as well as serine and cysteine proteases that have the capacity to degrade intact or structurally altered forms of collagen (18,60). Although our in vitro studies indicate that MMP-2-mediated degradation of collagen can lead to the generation of low molecular weights fragments recognized by mAb XL313, the precise mechanism by which the RGDKGE collagen epitope is generated in vivo is not completely understood.…”

Roles of NGAL and MMP-9 in the tumor microenvironment and sensitivity to targeted therapy

“…Tissue infiltrating neutrophils have been shown to be an important source of MMP-9 in the tumor microenvironment [147]. C-X-C motif chemokine 12/C-X-C chemokine receptor type 7(CXCR7) has been shown to regulate breast cancer metastasis by enhancing expression of MMP-2, MMP-9 and vascular cell-adhesion molecule-1 (VCAM-1).…”

Neutrophils: Critical components in experimental animal models of cancer

“…Also in transplantable tumor models of murine melanoma (B16F10), fibrosarcoma (L929), Lewis lung carcinoma (LLC) and human prostate cancer cells (PC-3), infiltrating neutrophils are the major source of MMP-9 [94]. Importantly unlike other immune cells that also produce MMP-9, neutrophils supply the tumor with a TIMP-free form of MMP-9 that more efficiently induces angiogenesis [94-97].…”